With the advent of mass personal computer usage, the incidence of repetitive injury disorders such as carpal tunnel syndrome has proliferated to the point of becoming the number one work related injury. It typically manifests itself with symptoms such as pain, numbness and/or stiffness in the hands, wrist, arm, shoulder and neck. Carpal tunnel syndrome has also been known to cause a loss of range of motion in the shoulder as well as loss of grip strength of the hand. Typically, treatments for carpal tunnel syndrome may range from noninvasive techniques such as physical therapy that includes joint manipulation, ultrasound, icing and electro-muscle stimulation, to ingestion of anti-inflammatory drugs, and to invasive procedures such as surgery for removing scar tissue within the wrist that impinges the median nerve. Therefore, a need exists to find means to permit a user to operate a computer mouse in a comfortable, ergonomic fashion that will prevent such disabling injuries.
A similar ailment, wrist tendonitis, has also been associated with computer use. The carpal tunnel is a narrow passageway in one's wrist through which the median nerve passes. This nerve carries sensations for the entire hand. It also affects the finger flexor tendons, which link one's fingers to the muscles in the person's lower arm. The tunnel is formed by walls of solid bone on three sides with the bottom enclosed by the transverse carpal ligament, a tough, inelastic cartilage. Tendonitis occurs when the tendons protect themselves from overuse. Each tendon is surrounded by a thick fluid-filled sac called a synovial sheath, which swells with extra fluid to protect the tendon. Such swelling is called tendonitis. When these sacs swell in the carpal tunnel, they can pinch the median nerve against the bone or carpal ligament. The result can be a loss of sensation in the hands and debilitating pain.
Computer use involves repetitive tasks like gripping, clicking, pushing and reaching for such items as the keyboard and mouse or other pointing device. The position of the user relative to these input devices requires extending upper extremities like the neck, shoulder, arms and hands from the desk chair to the mouse. A lack of optimum positioning, coupled with the highly repetitive nature of mouse use, may result in the aforementioned cumulative trauma injury. Efforts to decrease the stresses on a computer operator usually start only after injury symptoms first appear. The need for preventive support of an operator's upper extremities and wrist become more evident as more repetitive motion/stress related injuries are diagnosed.
Basic use of a computer mouse on a surface like a table requires positioning the user's hand in a generally horizontal plane. Such positioning may cause tendons in the hand to lie strained resulting in user discomfort. Further use in that position exacerbates the discomfort and may result in irritations of the carpal tunnel in some users. An invention is needed that allows a user to grasp the mouse with the wrist in a more natural upright position. Such an invention should reduce the stress on and swelling of the synovial sheath, thereby reducing the chance of sustaining a repetitive stress injury.
Tables exist that mount to the arm of a desk chair. But such tables do not typically tilt to the right or left about the X-axis, or in the same plane as the Z-axis. The parent invention creates a more neutral, upright position for the computer user's hand, wrist and forearm when using a mouse to alleviate tensions on the carpal tunnel. With the further adjustments of the present invention, it is possible to situate the user's elbow below their shoulder reducing at least some of the pressures exerted on a user's neck muscles.
Other devices involve more complex systems and may require specialized chairs. For example, U.S. Pat. No. 5,884,974 (Bergstem et al) describes a chair having supporting armrests that are adjustable in height, pivotable and longitudinally slidable. Unlike the parent invention, this device neither rotates the wrist into a natural position. Nor does that chair position a computer user's elbow below the shoulder.
U.S. Pat. No. 6,648,282 (Sykes) also fails to rotate a computer user's hand, wrist and forearm to a more natural upright position.
U.S. Pat. No. 5,730,408 (McAllister, et al) describes a workstation support for a keyboard and mouse. That device does not position the user's wrist in a preferred natural position. Instead, it forces the user to lean forward in the chair placing greater stress on his/her upper back and neck.